A patentee who brings a patent infringement lawsuit bears the burden of proving infringement by a preponderance of the evidence. Many patent infringement cases arise in the context of a declaratory judgment action, where an accused infringer brings suit and asks the court to declare the absence of infringement. Who bears the burden of proof in such cases, the declaratory judgment plaintiff or the patentee? As reported last week, in Medtronic, Inc. v. Mirowski Family Ventures, LLC [an enhanced version of this opinion is available to lexis.com subscribers], the U.S. Supreme Court held that it is the patentee who bears the burden of proving infringement.

Mirowski and related entities licensed Medtronic under certain Mirowski patents. During the term of the license, Mirowski notified Medtronic of its belief that certain additional Medtronic products infringed two of its patents. Medtronic brought a declaratory judgment action to assert that the accused products did not infringe or that the patent claims in question were invalid. The parties disagreed as to which party bore the burden of proving infringement. The Court of Appeals for the Federal Circuit held that Medtronic, as plaintiff in the lawsuit, bore the burden of proving that it had not infringed the Mirowski patents. Medtronic then sought and was granted a writ of certiorari.

On January 22, 2014, a unanimous Supreme Court reversed, holding that the burden of proof remains with the patentee. The Court observed that a patentee ordinarily bears the burden of proving infringement, and noted that the Declaratory Judgment Act was intended to provide a procedural mechanism for resolving disputes, while leaving the substantive rights of the litigants unchanged. Because the burden of proof is a substantive aspect of a claim for relief, reasoned the Court, the fact that the case arises as a declaratory judgment rather than as an infringement claim should not alter the allocation of the burden of proof.

The Court also identified several “practical considerations” as support for its conclusion. For example, if the burden of proof were on the declaratory judgment plaintiff, the Court hypothesized a situation where a declaratory judgment plaintiff lost at a first trial against a patentee, but won at a subsequent trial brought by the same patentee. In such case, reasoned the Court, the outcome would leave the parties and interested members of the public uncertain as to the true scope of the patent. The Court further found it unduly complex if the declaratory judgment plaintiff were forced to prove a negative, especially because the plaintiff would find it “difficult . . . to understand upon just what theory the patentee’s infringement claim rests.”

The Medtronic case resolves a longstanding procedural question and is a significant decision for clients who are involved with declaratory judgment actions.